The invention relates to a side-bar chain for infinitely variable cone-pulley transmissions which chain is composed of joint pieces connecting individual chain links and formed as pairs of rocker pieces pushed into apertures of the side-bars. The end faces of the rocker pieces transmit the friction forces between the friction pulley sheaves and the side-bar chain, and the rocker pieces are connected with associated side-bars with a shape-locking securing in rotation.
Such side-bar chains are known in many forms. By way of example reference may be made to German Pat. Nos. 1,065,685, 1,119,065, 1,302,795 and 2,356,289. It also appears from these printed documents that the chains can be assembled in a double side-bar structure, as disclosed in German Pat. No. 1,065,685, or a triple side-bar structure, as disclosed in German Pat. No 1,119,065, and shown in FIG. 14 thereof, where the double side-bar structure, with greater intervals of the pairs of rocker pieces in the running direction, is of narrower construction transversely of the running direction, while the triple side-bar structure, while resulting in a greater width transversely of the running direction of the chain, on the other hand renders possible a reduction in the intervals of the pairs of rocker pieces, that is a reduction of the chain pitch.
This chain pitch is important in several respects. Firstly, the number of the pairs of rocker pieces possible per unit of length of the chain, and thus the number of their end faces, determines the friction force which can be transmitted between friction pulley sheaves and chain. Next the chain pitch considerably determines the behavior of the chain as regards noise, since the entry of the rocker pieces between the cone pulley sheaves involves an impact-type noise which becomes the louder the greater is the chain pitch. Finally, in the case of a coarse chain pitch, the course of the chain in the looping arc between the cone pulley sheaves is made very polygonal, that is to say has relatively great breaks in the force direction, which naturally has an unfavorable effect.
For these reasons the chains of triple side-bar structure would appear preferable. However these chains are not used in practice, since in comparison with chains of equal performance of double side-bar structure they have a width which is half again as great transversely of the running direction. Because of the correspondingly increased chain weight, this leads to increased loading by centrifugal force and moreover, by way of the increased distance between the cone pulleys, has an effect upon the structural size of the entire transmission. The avoidance of these disadvantages predominates by far in comparison with the considerations discussed in connection with the chain pitch.